1. Field of the Invention
The field of the present invention is that of turbine engines and, more particularly, that of producing the high-pressure turbine blades for these turbine engines.
2. Description of the Related Art
A turbine engine for an aircraft generally comprises, from upstream to downstream in the direction of gas flow, a fan, one or more compressor stages, such as a low-pressure compressor and a high-pressure compressor, a combustion chamber, one or more turbine stages, such as a high-pressure turbine and a low-pressure turbine, and a gas exhaust pipe. A turbine may be associated with each compressor, the two being connected by a shaft, thereby forming, for example, a high-pressure (HP) core and a low-pressure (LP) core.
The turbine blades are parts that are subjected to very high temperatures and high mechanical stresses due to the centrifugal force acting thereon. In particular, the performance of modern engines dictates that the temperature to which the high-pressure turbine blades are subjected be as high as possible. For this reason, these blades are typically made of a metal material, but it would be beneficial for these blades to be made of a composite material and, in particular, a ceramic matrix composite (CMC). In fact, the advantage of CMC parts is their low density and their excellent temperature resistance. Their main shortcoming, conversely, is that they are less resistant to stresses and have a propensity to delustre; this makes it difficult to use them for turbine blades.
Work was first carried out to use this material in designing LP turbine blades, as in patent application FR2943942 filed by the applicant, since such blades are subjected to comparatively lower temperatures. However, it would be beneficial to also use this technology for HP turbine blades. This would thus make it possible to limit the mass of the blades and, in turn, that of the discs supporting said blades, and to reduce the ventilation flow rate and/or to increase the service life of these blades and discs.
In addition, European patent application EP 2077376 is known, which describes a hollow turbine engine blade of which both the vane and the root are made of composite material. This document describes how the root of the blade is formed and the shape assigned thereto; it does not describe how the vane of the blade is produced, apart from specifying that it is made of composite material. In particular, it is not indicated how the sheet used to produce this vane is oriented. EP 2363574 is also known, which describes a full blade, the vane of which is composed of fibres having a substantially radial orientation.
One problem encountered when adapting CMC technology for the production of HP turbine blades is the small size of the blades and the high cooling flow rate passing therethrough. It is thus difficult to produce said blades from composite material while leaving an internal cavity.